The present invention relates to a device in accordance with the preamble of claim 1.
The present invention relates to a device for processing semiconductor wafers, comprising at least one processing chamber with an gaslock system, a reactor, as well as feed and removal means for transferring said semiconductor wafers to and from the said reactor, being arranged in the said at least one processing chamber.
A device or this kind is known from U.S. Pat. No. 5,407,449 in the name of the applicant. In this device, a number of processing chambers is arranged around a centrally disposed distributing system or robot structure. From this centrally disposed robot, semiconductor wafers are transferred onto turntables which are situated in each of the processing chambers. In general, this takes place by the transfer of semiconductor wafers arranged in cassettes in the feed station or in a boat on a turntable in one of the processing chambers to a boat arranged a turntable in the other of the processing chambers.
A processing operation is carried out in each processing chamber, such as the doping of specific substances and the removal and/or application of (parts of) layers at elevated temperature. It is then necessary to allow the wafers to cool under controlled conditions before further processing operations can take place. Cooling of this nature may take place inside the processing chamber in question, but may equally be carried out in another processing chamber.
In the art, there is a constant desire to enlarge the semiconductor wafers further, i.e. for ever more extensive integration. As a result, the value of a series of semiconductor wafers in a boat is constantly increasing, especially for small batches, and the financial risk associated with the failure of a specific processing operation is constantly rising. Moreover, there is a demand for the capacity of devices for processing semiconductor wafers to be increased.
One proposal in the prior art comprises the provision of different processing chambers, which are each closed and each perform the same processing operation. This means that a specific series of semiconductor wafers is fed to a processing chamber, where it undergoes a processing operation, while another series is fed to another processing chamber, where it undergoes the same processing operation. This provides an initial saving, since it is possible to make use of the common robot or the common distributing system and the common feed and removal from the system. It has been found that, although a system of this kind functions in certain cases, primarily where the residence time of the semiconductor wafers in the processing chambers is relatively long, in many applications the capacity of the distributing system, and more particularly the robot arranged therein, forms the bottleneck in the capacity of a device of this kind.
By also placing a boat with semiconductor wafers to be processed in the xe2x80x9cwaiting positionxe2x80x9d in a system of this kind, three positions are provided in a processing chamber of this kind, with the result that optimum utilization can be achieved. This means that three boats are present on a turntable. It will be understood that this number can be greater.
U.S. Pat. No. 5,464,313 discloses a stand alone oven assembly comprising two adjacent ovens which are provided with boats of wafers by a single, linear operating system. This structure is not a space-saving one, and also cannot be used in the compact cluster structure as described in U.S. Pat. No. 5,407,449.
The object of the present invention is to increase further the processing capacity of a device described above without it being necessary to extend the distributing system and while utilizing the floor area in question as efficiently as possible. This is important because the device will generally be arranged in a clean room.
An object of the invention is a device for processing semiconductor wafers including a processing chamber. The processing chamber comprises a central distributing system for transferring wafers between a store or another processing chamber and a boat on a turntable in the processing chamber. The processing chamber is configured to be closed with respect to the central distributing system. The processing chamber comprises further a first reactor, first feed and removal means for transferring the boat with the semiconductor wafers from the turntable into the first reactor arranged in the processing chamber, at least a second reactor arranged within the processing chamber, and second feed and removal means for transferring the semiconductor wafers from the turntable into the second reactor.
Surprisingly, it has been found that arranging two reactors in one processing chamber, i.e. no longer separated by the distributing system, allows the capacity to be increased considerably without substantially enlarging the floor area. Moreover, it is not necessary to provide separate retention for the reactors, so that the cost price is reduced. This inventive idea may optionally be combined with further processing stations, as known for example from U.S. Pat. No. 5,407,449. According to the invention, when feeding semiconductor wafers to the boat on the turntable of the processing chamber in question, preferably a first series of semiconductor wafers is processed by the first reactor and a second series of semiconductor wafers is processed by the second reactor, in which case the processing operation in these two reactors may be identical. The processing chambers can be loaded using the turntable structure which is known from U.S. Pat. No. 5,407,449, i.e. it is possible to use a turntable which has three positions for the boats. In this case, if the cooling is important, a substantial part of the waiting time of the semiconductor wafers is taken away before they can be removed from the reactor. This can be resolved, on the one hand, by providing a turntable with four positions for the cassettes, but in other cases this will not be important, because the ratio between the cooling time and the processing time is such that the processing time is longer than half the cooling time, so that sufficient time remains to take the cooled semiconductor wafers out of the processing chamber and to replace them with wafers to be processed.
The reactors may comprise any type of reactor, but preferably comprise two processing ovens. It will be understood that the idea according to the invention can be extended to a processing chamber in which there are three or more reactors. In that case, the turntable will have to have more than three positions, or else the structure with the turntable will need to be designed differently.
Obviously, in the structures described above, as in U.S. Pat. No. 5,407,449, in addition to a turntable there is also a lifting means for each reactor in order to remove the relevant boat from the turntable and introduce it into the reactor and then to remove it again from the reactor.